Recent switcheR here. All of the above responses are very helpful. There is a free option to your Document concerns that wasn't mentioned. Openoffice will open MS word files and save that way as well. You just pick the type of file you want it to save as. I have iWork and honestly have not used it at all. I continue to use oppenoffice for spreadsheets and creating documents. Eventually I will have to use keynote for presentations, and that is found in iWork.

As for the finder concerns, think of it as the search option found under My Computer on windows. But better and easier. It finds things that you can't remember where they are basically. And help you stay organized.

On apple.com there are tutorials available on everything you have questions about. There are links on the homepage at the bottom that say New to Mac, they are a great help to newbie questions (like the kind instill have haha).